Nowadays, much (personal) data is stored on memory modules embedded in systems, such as smartcards for pay-TV or electronic purses. In order to protect data, security should be as high as possible. Typically, the data is protected from external read-out with a secure key. Once the key is known, the data can be read out. The external read-out of data by decryption of the data is known as a non-invasive attack.
In invasive attacks the chip is de-packaged, where the goal is direct read-out of the data in the memory or disabling the key by UV radiation. Both approaches require removal of the chip package and sometimes even the passivation layers. Generally, it is quite difficult to protect against these kinds of physical attacks. More information on tamper resistance of ICs can be found in: USENIX Association, “Tamper Resistance—a Cautionary Note”, The Second USENIX Workshop on Electronic Commerce Proceedings, Oakland, Calif., Nov. 18-21, 1996, pp 1-11, ISBN 1-880446-83-9 (also available at the following site: www.cl.cam.ac.uk/˜rja14/tamper.html).
Many methods to protect against non-invasive attacks are known and most disclosures about IC security focus mainly on these attacks. For the protection against invasive attacks fewer solutions are known. Meanwhile, history has shown that hackers come up with more clever attack techniques regularly.
In view of the above mentioned situation there is a need for an alternative type of tamper protection.